High quality illumination is essential in medical applications, particularly in a surgical environment. Uneven illumination over the field of view may cause a surgeon to perceive problems that do not actually exist in the patient. Further, illumination anomalies and artifacts clutter and may distort the doctor's field of view, and may thus cause the doctor to miss details critical to the doctor's performance. Stray light beyond the desired illumination field distracts the doctor. Also, it is highly desirable to be able to adjust the spot of the illumination, so that only the area under consideration is seen by the doctor. Thus, medical professionals have long sought the best possible illumination in pursuit of the best possible outcomes.
With the advent of high power, light emitting diodes (LEDs), medical illuminators have used these devices as a light source. The light emitting diode based systems have the difficulty that the light source, the light emitting diode die, is typically square. Moreover, the top of the light emitting diode die invariably has some form of connecting wires, metallization or other structures to conduct electricity into the silicon. These conductors are generally not visible in typical light emitting diodes deployments where light emitting diodes illuminate a broad field. In a surgical illuminator, however, that images the light emitting diode onto the viewing surface, the light emitting diode die conductors are clearly visible and they degrade the light quality. The light emitting diode based surgical illuminators typically image the light emitting diode die onto the viewing plane to achieve a small spot size, and thus the spot is either a square or show at least the remnants of that square. Most doctors that use illuminators have been trained using fiber-optic illumination systems that emit circular illuminated spots. They are used to seeing bright circles, and prefer them.
While light emitting diodes are generally more efficient than incandescent sources, they still generate considerable heat. Inefficient dissipation of the heat can cause failure or degradation of the light emitting diode. Further, if the case of the illuminator gets hot, it can become difficult to touch. This can cause operator discomfort, as well as making it difficult to adjust or aim the beam by touching and moving the case.
What is needed is a surgical illuminator that avoids the deficiencies of the prior art.